A known problem is interference to the reception of a desired radio signal caused by a secondary use radio signal. For units of two systems that operate using signals whose frequency bands overlap, interference is usually controlled by a government agency that restricts operations of units of the two systems to geographic areas that prevent such interference.
However, radio spectrum is very valuable and there are circumstances for which units of two systems that have overlapping frequency bands could operate without substantial interference. One example of these circumstances is a short range system that includes units that operate at very low power level in a region that is near, but not within a defined operational range of a wide area system. For a region within which the signal level transmitted by a unit of the wide area system is, to a high degree of likelihood, too low to be useful, the probability of interference to units of the wide area system by units of the short range system could be acceptably low.
This type of situation is proposed for use in the United States of America for commercial broadcast television transmissions and units identified herein as dynamic spectrum sharing units. Such dynamic spectrum sharing units would operate on commercial broadcast television frequencies but would have a built in control to prevent them from transmitting unless a probability of interference to television reception was acceptably low.
However, techniques currently proposed to accomplish the control of transmissions of units of a second system to achieve a desired certainty of non-interference to units of a first system severely limit the usefulness of dynamic system sharing.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.